The rotor craft of the type concerned herein is a gyroplane, which has wings, a means of forward thrust other than the rotor, and a rotor. The rotor provides most of the lift during short or vertical takeoffs, slow speed flight, and landings, and the wings provide most of the lift during cruise conditions. For a short or zero roll takeoff, the pilot pre-rotates the rotor to a selected speed. While pre-rotating, the pilot maintains the collective pitch near zero. The collective pitch refers to the angle of attack of the blades relative to the plane of rotation. At zero collective pitch, the leading and trailing edges of the blades are in a common plane with the plane of rotation.
When ready for liftoff, the operator releases the clutch driving the rotor so it freewheels and increases the collective pitch, which tilts the leading edge of each blade upward relative to the trailing edge. The rotor has tip weights to provide high inertia, and the inertia drives the rotor which causes the aircraft to lift while a means of thrust propels the aircraft forward. The operator gradually reduces the collective pitch as the aircraft picks up speed. The operator also decreases the aft tilt of the rotor, which reduces the airstream flowing through the rotor, thus decreasing the rotational speed. At cruising speeds and at an advance ratio greater than about 0.7, the collective pitch is generally between 1.5 and minus 0.5 degrees, and the rotor provides very little of the lift. The airstream flowing through the rotor causes the rotor to auto-rotate at a selected slow rotational speed.
When landing, the operator tilts the rotor aft, which causes the rotor to speed up. The operator also increases the collective pitch, causing the rotor to assume more of the lift required for the aircraft.
Flying a gyroplane as described requires the operator to adjust the collective pitch from near zero, during pre-rotation, to a high level for takeoff and landing, and again to between 1.5 and minus 0.5 degrees at cruising speeds. Some skill must be acquired in order to properly adjust the collective pitch and the operator must remain aware of the necessity of making the pitch changes.